Rechargeable batteries such as batteries made up of many lithium-ion cells can be used in many applications, including for example, electric propulsion vehicle (“EV”) and hybrid electric vehicle (“HEV”) applications. These applications often require advanced battery systems that have high energy storage capacity and can generate large amounts of heat that needs to be dissipated. Battery thermal management of these types of systems generally requires that the maximum temperature of the individual cells be below a predetermined, specified temperature.
Cold plate heat exchangers are heat exchangers upon which a stack of adjacent battery cells or battery cell containers housing one or more battery cells are arranged for cooling and/or regulating the temperature of a battery unit. The individual battery cells or battery cell containers are arranged in face-to-face contact with each other to form the stack, the stack of battery cells or battery cell containers being arranged on top of a cold plate heat exchanger such that an end face or end surface of each battery cell or battery cell container is in surface-to-surface contact with a surface of the heat exchanger.
Heat exchangers for cooling and/or regulating the temperature of a battery unit can also be arranged between the individual battery cells or individual battery cell containers that form the stack, the individual heat exchangers being interconnected by common inlet and outlet manifolds. Heat exchangers that are arranged or “sandwiched” between the adjacent battery cells or battery cell containers in the stack may sometimes be referred to as inter-cell elements (e.g. “ICE” plate heat exchangers) or cooling fins.
For both cold plate heat exchangers and inter-cell elements (or ICE plate heat exchangers), temperature uniformity across the surface of the heat exchanger is an important consideration in the thermal management of the overall battery unit as the temperature uniformity across the surface of the heat exchanger relates to ensuring that there is a minimum temperature differential between the individual battery cells in the battery unit.
During cooling mode, it is generally understood that the coolant travelling through the heat exchangers removes thermal energy from the battery cells that make up the battery units. Therefore the temperature of the coolant tends to increase along the length of the fluid channel. Given that the surface temperature of the cold plate or ICE plate heat exchanger will generally be proportional to the temperature of the coolant or fluid travelling through the heat exchanger, the temperature of the coolant will be cold (or cooler) at the inlet end of the heat exchanger and warmer (or hotter) near the outlet end of the heat exchanger resulting in an inherent temperature differential across the surface of the heat exchanger. As a result of the inherent temperature differential across the surface of the heat exchanger, battery cells arranged proximal to the inlet end of the heat exchanger will be subject to a lower coolant temperature than battery cells arranged proximal to the outlet end of the heat exchanger resulting in a potential temperature differential between the individual battery cells within the overall battery unit which, generally, is considered undesirable. Since temperature uniformity across the surface of the heat exchanger allows for more consistent cooling or thermal management of the overall battery unit, it is desirable to provide heat exchangers that offer improved temperature uniformity across the heat exchange surface of the heat exchanger in an effort to provide for more consistent cooling to the individual battery cells or battery cell containers that form the overall battery module across the entire surface of the heat exchanger plates. As well, given that the overall size of battery units can vary depending on the particular application, the ability to form heat exchangers of this type having various sizes without requiring costly tooling changes is also desirable.